1. Field of the Invention
The present invention relates to an isobutylene base polymer having a functional group and a process for preparing the same.
2. Description of the Prior Art
A polymer having a vinyl group at its molecular chain end or in a grafted chain is useful as a raw material of an adhesive, a modifier, a coating material, a sealing material and the like.
As a preparation method an isobutylene base polymer having a terminal functional group which is one of the above described polymers, the Inifer method is known from U.S. Pat. No. 4,276,394, which method comprises cationically polymerizing isobutylene in the presence of 1,4-bis(.alpha.-chloroisopropyl)benzene (hereinafter referred to as "p-DCC") as an initiator/chain-transfer agent and BCl.sub.3 as a catalyst.
It is also known that the isobutylene base polymer having chlorine atoms at both chain ends as produced by the Inifer method or after purification can be converted to a polymer having allyl groups at both chain ends through the reaction of the isobutylene base polymer with allyltrimethylsilane in the presence of BCl.sub.3 and TiCl.sub.4 as a further catalyst (see Japanese Patent Kokai Publication No. 105005/1988 corresponding to U.S. Pat. No. 4,758,631).
However, by the above method, the allyl groups are introduced only at the chain ends. In order to introduce more than two allyl groups in one molecule, a compound having two or more polymerization initiating sites such as p-DCC should be used.
An isobutylene base polymer having an unsaturated group is obtained by copolymerizing isobutylene and a conjugated diene. But, a produced polymer has inferior weather resistance since an unsaturated group due to 1,4-addition is introduced in a main chain. When isobutylene and the nonconjugated diene are copolymerized, a produced polymer has no unsaturated group, but the polymerization reaction does not proceed smoothly.